This invention relates to support apparatus and, more particularly, to apparatus for supporting a carriage about an elongate shaft for linear movement of the carriage along the shaft.
Carriage support apparati of the type above-described have been found useful in many different machine environments where it is necessary to move an assembly linearly with respect to a stationary member. An example of a machine having need for such a support apparatus is a high speed serial printer of the type in which a printing assembly comprising a rotatable print print wheel, a hammer for striking a selected character element on the wheel and a ribbon cartridge is mounted to a carriage, and in which the carriage is supported for movement along a pair of rods or shafts by a respective pair of support apparati. In accordance with known high speed serial printers of this type, the support apparati employed generally each include a set of roller bearings, means for mounting the bearings to the carriage and means for biasing the bearings against the respective shaft.
There are certain inherent disadvantages from the use of roller bearings and biasing means in a carriage support apparatus. For example, each roller bearing presents a point contact with the associated shaft at any instant of time and is thus subject to wear at the line apex of the bearing. Further, the carriage may be subject to rocking about a pivot line perpendicular to the axes of the shafts when moved along the shafts at high speeds due to the biasing of the bearings against the shafts. Such rocking is especially undesirable in the context of a printing machine where print quality might be adversely impaired thereby. Additionally, the need for a biasing means for each of a plurality of roller bearings adds to the cost and complexity of the support apparatus.
Accordingly, it would be desirable to provide a carriage support apparatus capable of supporting a carriage about an elongate shaft for linear movement of the carriage along the shaft, which apparatus is substantially free of the above disadvantages.